20 



CIRCULAR 2 70, U. S. DEPARTMENT OF AGRICULTURE 



combating powdery mildew or scab (table 1, p. 71), are valuable in 

 destroying the young mites. These sprays should be applied just 

 before the blossoms open and again as a calyx application. 



It is often necessary to use lime-sulfur solution in the dormant- 

 season application on account of the presence of other insects that 

 are best combated with that material. If such insects are on the trees, 

 or if the mites have not been otherwise controlled, a veiy effective 

 measure consists in using oil in one or more of the summer spravs. 

 The treatment may be combined with that for the codling moth bv 

 simply adding 1 to 1% gallons of a standard summer-oil emulsion to 

 100 gallons of the lead arsenate spray. Preferably this should be 

 done before July, unless previous applications of lime-sulfur solution 

 make it inadvisable. Oil should not be used in summer spravs less 

 than 60 days after a lime-sulfur application, because of the danger of 

 burning the foliage. 



Slimmer treatment is necessary for the Pacific mite, since this 

 species is usuaUy not on the trees when the earlier sprays are made. 

 Lime-sulfur solution .in the "pink" spray at 2 or 3 gallons of the con- 

 centrate to 100 gallons of water, followed by colloidal or elemental 

 sulfur at 3 to 5 poimds to 100 gallons added to the calyx and first 

 cover sprays as applied for the control of the codling moth* constitutes 

 the most effective control for this mite. This is because the sulfur 

 collects in the webbing and the fumes kill the mites running about hi 

 it, including the yoimg as they hatch. Sulfur is much less effective 

 against those species that do not spin webs. 



Summer spraying for red spiders must be extremely thorough, as 

 the spiders infest the entire tree, and portions not sprayed & oit en 

 harbor enough spiders to reinfest the tree in a short time. 



Pear Leaf Blister Mite 



The pear leaf blister mite {Eriophyes pyri Pgst.) lives in the buds, 

 foliage, and fruit of apple and pear trees. It produces smaU galls or 



blisters on the leaves. At first 

 these galls are greenish or reddish, 

 but later turn brown and cause 

 dead areas. These areas may 

 have an appearance similar to 

 that of apple scab but may always 

 be identified by the small round 

 bole which will be found on 

 the under surface of the leaf ap- 

 proximately in the center of each 

 blister (fig. 21). Since the mites 

 begin feeding in the leaves before 

 these are fully opened, the new 

 leaves show the blisters at once; 

 and if the mites are numerous, 

 many of the leaves later dry and 

 drop off. The fruit of the apple 

 is more seriously affected than 

 that of the pear; it is attacked 

 when it is young, and the injuries 

 Figure 21.— Apple leaf infested wit] cause mature fruit to be russeted 

 pear leaf blister mite. or deformed (fig. 22) and some- 



